Add ability to rename System.Service scripts

<Provides>
  <COMAR script="iscsi-service.py" name="iscsi">System.Service</COMAR>
  <COMAR script="iscsid-service.py" name="iscsid">System.Service</COMAR>
</Provides>

Will register two separate system services called respectively "iscsi" and "iscsid". This way
we don't have to split packages to give them separate names or to provide more than 1 services
in a sub-package.

pisi-spec.rng

@@ -1420,6 +1420,9 @@
         <optional>
             <attribute name="script"/>
         </optional>
+        <optional>
+            <attribute name="name"/>
+        </optional>
     </define>
 
     <!-- Conflicts -->